Pneumatic tire

Abstract

The present invention provides a pneumatic tire having: a circumferential groove continuously extending in the tire circumferential direction in a ground contact surface of a tread portion; and a resonator provided in a land portion and constituted of a resonance cell portion opened to a ground contact region at a position distanced from the circumferential groove and a siping portion making the resonance cell portion communicate with the circumferential groove, wherein change in a tread pattern as time lapses can be alleviated without scarifying an effect of reducing pipe resonance sounds. Specifically, an opening width of the siping portion at the ground contact surface of the tread portion is designed to change in the longitudinal direction thereof such that the opening with is relatively narrow on the side of the circumferential groove and relatively wide on the side of the resonance cell portion.

1. A pneumatic tire having: a circumferential groove continuously extending in the tire circumferential direction in a ground contact surface of a tread portion; and a resonator provided in a land portion and constituted of a resonance cell portion opened to a ground contact region at a position distanced from the circumferential groove and a siping portion for making the resonance cell portion communicate with the circumferential groove, characterized in that:
 an opening width of the siping portion at the ground contact surface of the tread portion is designed to change stepwise in the longitudinal direction thereof such that the opening width is relatively narrow on the side of the circumferential groove and relatively wide on the side of the resonance cell portion, and 
 the resonance cell portion terminates in the land portion without communication with an another adjacent circumferential groove. 
 
     
     
       2. The pneumatic tire of  claim 1 , wherein, provided that the length in the tire circumferential direction and the length in the tire widthwise direction of the resonance cell portion of the resonator are L 3  and L 4 , respectively, L 4  is not larger than L 3 . 
     
     
       3. The pneumatic tire of  claim 1 , wherein the ground contact surface of the tread portion is provided with at least one shoulder groove extending from the circumferential groove toward the outer side in the tire widthwise direction thereof to a position beyond a ground contact end of the tread. 
     
     
       4. The pneumatic tire of  claim 1 , wherein a sectional area of a face of the resonance cell portion, which face is orthogonal to the extending direction of the resonance cell portion, is larger than a sectional area of a face of the siping portion, which face is orthogonal to the extending direction of the siping portion, and the siping portion has on the groove bottom side thereof an enlarged portion having a larger groove width than the opening width of the siping portion. 
     
     
       5. The pneumatic tire of  claim 1 , wherein a sectional area of a face of the resonance cell portion, which face is orthogonal to the extending direction of the resonance cell portion, is larger than a sectional area of a face of the siping portion, which face is orthogonal to the extending direction of the siping portion, and the depth of the resonance cell portion is not larger than the width of the resonance cell portion at the ground contact surface of the tread portion. 
     
     
       6. The pneumatic tire of any of  claim 1 , further comprising:
 at least one row of rib-like land portions adjacent to the circumferential groove, 
 wherein a plurality of the resonators are provided along the tire circumferential direction in the rib-like land portion, and 
 each resonator has a first end and a second end defining a length in the tire circumferential direction of the resonance cell portion, the siping portion extends from the second end of the resonator in the direction away from the first end of the resonator, and the first end of one resonator and the second end of another resonator adjacent to the one resonator in the tire circumferential direction are aligned with each other on the same line in the tire widthwise direction. 
 
     
     
       7. The pneumatic tire of  claim 1 , further comprising:
 at least one row of rib-like land portions adjacent to the circumferential groove, 
 wherein a plurality of the resonators are provided along the tire circumferential direction in the rib-like land portion, and 
 each resonator has a first end and a second end defining a length in the tire circumferential direction of the resonance cell portion, the siping portion extends from the second end of the resonator in the direction away from the first end of the resonator, and, when viewed in the tire widthwise direction, the resonance cell portion of one resonator at least partially overlaps the siping portion of another resonator adjacent to the one resonator in the tire circumferential direction. 
 
     
     
       8. The pneumatic tire of  claim 1 , further comprising:
 at least one row of rib-like land portions adjacent to the circumferential groove, 
 wherein a plurality of the resonators are provided along the tire circumferential direction in the rib-like land portion, and 
 each resonator has a first end and a second end defining a length in the tire circumferential direction of the resonance cell portion, the siping portion extends from the second end of the resonator in the direction away from the first end of the resonator, and the sectional area in the tire widthwise direction of the resonance cell portion gradually decreases toward the first end of the resonator. 
 
     
     
       9. The pneumatic tire of  claim 1 , wherein a length (L 1 ) of the resonance cell portion along the widthwise direction center line LN thereof is larger than a length of (L 2 ) of the siping portion along the widthwise direction center line LN thereof. 
     
     
       10. The pneumatic tire of  claim 1 , wherein a depth (D 1 ) of the resonance cell portion is larger than a depth (D 2 ) of the siping portion.